For many years centralised oil mist lubrication systems have been used to provide continuous lubrication to rotating equipment bearings. Oil mist lubrication gives benefits over other lubrication methods, providing:                reduced heat generation by the rotating elements        reduced equipment power consumption        reduced wear of the rotating and stationary elements        lower oil consumption, and        positive pressurisation of the bearing housing to prevent the ingress of particulate contaminant and moisture.        
Oil mist lubrication is of use in many situations including with modern bearing seals such as magnetic face seals.
However, oil mist systems may be difficult to justify because of their cost, complexity and commissioning time.
U.S. Pat. No. 5,318,152 discloses a lubricating system in which a plurality of bearings of one or more bearing equipped items are lubricated from a centralised oil mist generator. This system includes an oil mist generator, a distribution assembly for distributing the oil mist from the oil mist generator to the bearings, a collective device for collecting excess oil and oil mist from the bearings and a return assembly through which excess oil and oil mist are returned to an oil mist collection/supply vessel for re-use.
This system therefore relies on components, which are additional to the bearing housing. This centralised approach is not only costly, as it requires the additional components, but it also:                takes up considerable physical space,        requires extensive commissioning time and expertise,        gives rise to costs to run distribution pipework, in industry, in excess of US$100 per foot, given all the resources required not only to plan and approve such a pipework network but also maintain it.        represents a compromise solution given that oil mist is distributed from a centralised system to multiple types of equipment, such as electric motors, pumps, and gearboxes. Since the lubrication requirements of each type of equipment vary with bearing size, number of rolling elements and speed of operation, a compromised/non-idealised oil mist flow must be selected. This also means that the base oil type selection has to be compromised, since some types of equipment require different oil characteristics, for example, gearboxes may need oil anti-spalling and/or wear properties, pumps may need reduced rust formation properties, and motors may need an oxidisation inhibitor.        when equipment is replaced with different sized equipment, centralised systems offer little flexibility, or oil misting conditions are never changed in practice to meet the requirements for the replaced equipment.        centralised systems, containing venturi/vortex generation heads are often over sized since engineers wish to anticipate the future additional equipment needs. Unfortunately, this creates a far from ideal operation, and mist delivery is compromised as large generator heads create larger oil mist particles which then coalesce in the pipework before reaching the equipment        coalescing oil can interfere with the mist distribution in a centralised oil mist system, leading to blockage at the source. Clearly as the centralised systems supply multiple pieces of equipment a blockage leads to these multiple pieces of equipment failing which is clearly a very risky and costly operation.        distribution pipework, from a centralised system, must be inclined from the source, so to allow coalesced oil mist to run back to the source under gravity. This requirement causes practical difficulties in an industrial plant with equipment positioned in different three-dimensional locations. It is practically impossible to implement a suitably inclined pipe distribution system, which satisfactorily meets this requirement.        centralised systems can only feed equipment in an approximate 500 m radius given that oil mist coalesces at the interior surface of the pipework prohibiting longer distribution runs.        multiple reclassifier nozzles lead to confusion, misapplication and installation errors. Many oil mist installations fail because of simple errors from the system suppliers and those involved in selection, set-up and configuration. Laws of probability state that complex systems create more problems. Centralised systems can only be described as complex.        